Grinding Disc VS Flap Disc For Lawn Mower Blade Sharpening

How to sharpen a lawn mower blade the easy way. In this video I test out traditional grinding disc versus various flap disc's of different grit levels on a 4.5 inch angle grinder to see what is the best to use for sharpening lawn mower blades.
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[@LawnCareBusinessSuccess]

Let me know in the comments below what your preferred method is to use to sharpen your lawn mower blades.

[@AlanCanon2222]

I particularly appreciate how complete and thorough the testing regime was here, including trying the various grits of flap disc. I am a trained scientist, not a mechanic, and this video reads like a well-written paper in experimental physics or observational astronomy. What I'm trying to say is that for a person of my background, this is effective technical communication of a very high level of quality. Thank you. This is going to be my next project. The house where I am staying has a janky old lawnmower that would barely run, and thanks to KZbin videos, I learned to clean the carb, change and gap the spark plug, and fix poor contact between the ignition coil assembly and the engine block (which was the real problem). I'd never gone this far into small engine repair before. It was hugely satisfying when the lawnmower fired up on the very first pull, after days of frustration. And it didn't struggle or hesitate, it now runs like it's supposed to. I couldn't believe it. I shut it down and let it cool off and started it again: this time it took two pulls, because I'd forgotten to push the primer bulb. And it STILL started and ran like gangbusters on the second pull. I know way more about computers and electronics than I do about engines, but thanks to KZbin videos like this I was able to apply the Scientific Method to get a dead engine running, and running quite well. The trick, like any other, is to identify and eliminate unknown variables. The carb and spark plug and fuel weren't the problem, but I didn't know that until I tackled each one in turn. Also, apart from buying tools like nutdrivers and a spark plug socket, I basically received a free education in those areas, which I never would have gotten if I had stumbled on the correct solution straight off the bat. The vibration from the blade is so bad that I'm worried it will shake the mower apart. So I am now moving on to blade sharpening and balancing. Fortunately, the same shed that furnished the mower also furnished no fewer than three electric angle grinders. I will follow the advice here and report back when I'm finished. I plan on just using a screwdriver for balance testing, I think I can probably at least get the blade closer to being into balance than it is now.

[@johns6816]

Us average guys should hold the blade in a vise and use both hands on the grinder. Definately going to try the flap wheels next time. For other newer users, higher grit numbers mean a less aggressive cut and a smoother finish. Thanks for making this a quick and to the point youtube!

[@LawnCareBusinessSuccess]

Thanks for watching.

[@bigmeltie1]

Unsafe method.

[@Justthemow]

God you people can’t possibly be serious with all this cry baby bull💩 we aren’t in kindergarten we don’t need people holding our hands to cross the street hood the blade in one hand use the grinder in the other and work

[@irbyboy2342]

I've been using the 40 grit one and absolutely love it I can see a big difference in cut quality I like for my work to look as good as possible

[@LawnCareBusinessSuccess]

Nice 👍 Thanks for watching

[@sptrader6316]

On a mower blade in fairly good shape, I always use a 60 grit flap disc, a 40 grit takes off too much material, if you're not careful. I used to use a grinding wheel but it's just too aggressive.

[@LawnCareBusinessSuccess]

Great tip. Thanks for watching.

[@DenCoDave]

The grinding wheel will cut on a circumfrence that will produce a concave blade profile and the flapper will produce a convex profile. For these geometries the difference is not much, but the convex profile will hold its edge longer. For the same orientation of the grinder for each disc type, the concave will be sharper though. Use the flapper disk and just adjust the grind angle if this is likely to be an issue.

[@LawnCareBusinessSuccess]

Thanks for watching and Sharing.

[@kansasgardener5844]

Remember people watching this video are going to do what they see! 1st the blade itself should be in a vice. 2nd you shouldn't be holding the grinder with one hand. 3rd grind away from the edge of the blade not towards it. Other than that great video. And don't forget the safety glasses. Lol

[@andre1987eph]

Hecho en Mexico 🇲🇽

[@bruceglisson1720]

You got be be frigging kidding

[@Justthemow]

You should change your name to Karen and then grow up adults can think for themselves self and I’ve been sharpening blades like this for 20 years with 0 problems

[@kansasgardener5844]

@@Justthemow Glad I could help out.

[@animal79thecat]

Fkin bullshyt

[@paulretzbach9583]

Flap disk with the All American Sharpener!! Works great

[@LawnCareBusinessSuccess]

Nice 👍 Those All American Sharpener jigs look very cool! Thanks for watching.

[@bltefft]

Me too.

[@Matt6593]

Nice interesting video. Like the style of your sharpening. Hands on quick sharpening.

[@johnmckee7937]

Mower blade sharpening is kinda like welding, 3 guys in a room you'll get 5 answers. I liked the comparison between disc and flap. Usually, videos show only one. I am going to try flap disc for myself! Since I'm a homeowner my blades don't get dinged only dull. I find a rotary tool works well, finish with file.

[@mudderD]

Fantastic video. Heading to the store now.

[@LawnCareBusinessSuccess]

Glad you found value in the video. Thanks for watching.

[@TahoeREServices]

I've just started sharpening my blades on zero turn mower. I notice there are videos showing blades placed on a nail afterwards to see if both sides of a blade are balanced. Do you recommend doing this? Making sure your blades are balanced? Secondly, should the 3 blades be placed back on the mower in any particular spin location? Thanks.

[@Grahams-Grass]

40 grit is the best way I have found... really cuts a nice clean edge 👌

[@LawnCareBusinessSuccess]

Nice! Thanks for sharing and watching.

[@davidwhitten4051]

Man you really should start grinding away from your body instead of going to your stomach, (for safety) but the flap does work tons better

[@LawnCareBusinessSuccess]

Thanks for your concern and I appreciate you watching.

[@oscartangoromeo003]

As long those flap disc doesn't get any structure malfunction on losing one or two of those flaps on that flap disc making it a gaps between those flap disc that will makes those gap catches and griping the blade and just used your imagination what happened afterwards depending on the angles and depending where the blade is facing..

[@sy73326]

That’s some brave @$$ sharpening right there

[@rooster3019]

I use the 40g with an All American jig to sharpen the blades for my Ventrac Tough Cut, really heavy commercial blade plus CW and CCW bevels. The 80g is OK for the commercial blades on my finish deck.

[@LawnCareBusinessSuccess]

Nice 👍 thanks for sharing and thanks for watching.

[@shulermilton1]

A vice and whatever is on the grinder at the time. I may start using flappers exclusively from now on

[@andrewsallee6044]

Is there a performance difference between the T-27 flat and T-29 beveled disks?

[@mrcruz956tx]

Nah the 29 is curved and the 27 is flat. Both can do the job but it’s a matter of preference. Flat discs are good for removing material on larger surface areas while curved ones (imo) allow for some precise sharpening at shorter angles than would be required with a flat one.

[@robertblalock5009]

Best way this, best way that..the very best way is not get cut or mangles by the sharp edges on the blade.

[@vosechu]

Aren’t you comparing a tired old disc to a brand new flap? I’d be interested to know if that makes a difference.

[@LawnCareBusinessSuccess]

I doubt it would make a difference. A grinding disc has that same grinding surface all the way through to the end even as it gets smaller. A flap disc is essentially sand paper and would lose grit as it gets used. So if anything it would be the reverse that would make a difference and I suspect a grinding wheel would last much longer than a flap disc but it doesn’t leave as nice of an edge. Thanks for watching.

[@mlhm5]

You only need a 60 grit flap disk to sharpen any mower blade.

[@georgedavall9449]

Flap disk, 60 grit Only way to go

[@LawnCareBusinessSuccess]

Definitely a good choice. Thanks for watching.

[@robertblalock5009]

Sharpen the contour of a mulch blade with curve in blade.

[@johnslawncaretips4103]

40 grit flap disc the best leaves a great finish

[@bottmar1]

People and their this is better, that is better. The FACT is that a grinding stone is better because is faster and far cheaper leaving an edge that is as sharp as you need it. It is pointless to have, what some people think is a razor edge, in the environment that a lawnmower blade spins in. Fussiness will get you nothing but less money in your wallet with the five times as much you will pay for flap discs. Go ahead and pay extra for an imaginary benefit if you hate your money so bad.

[@bottmar1]

The guy that says going away from the edge doesn't know what he is talking about. Grinding towards the edge leaves less metal rolled over that has to be ground off. There is no reason to have a rounded edge with a grinding wheel. Use the grinding wheel correctly.

[@robertflanagan6117]

your removing to much material from the blade waring down blade fast. just a 1-2 pass is all thats need.

[@robertmceuen3630]

Flap wheel gives a much more refined edge. 40 or 60 grit is fine. No grinding wheel. You're sharpening, not grinding.

[@BillChase-qm8ud]

flap disk leaves a rounded edge

[@jonfranklin9361]

Flap disc my preferred method. More aggressive, faster. Makes them razor sharp. Great channel. Happy Mowing

[@LawnCareBusinessSuccess]

Yes I can definitely see why it’s your preferred method. It’s now mine too. Thanks for watching.

[@laurapalmerTDGE]

​@@LawnCareBusinessSuccess - Thanks for sharing big boy. I've made the very bad mistake previous month's by using a regular hard disc. A 60 grit flap made it so easy. From now on I sharpen my 2417 honda riding mower blades every few weeks. No more struggling! Cheers.

[@toddgill2338]

Thanks so much for this review! I am switching to flap disks too, as a residential consumer..... great comparison between the 'grits.'

[@LawnCareBusinessSuccess]

Glad it helped. Thanks for watching.

[@NZsarge1]

Cheers for that, was just contemplating wether a flapper disc would be suitable for this task exactly and it look like I’m getting myself some 80 grit flapper discs 👍🏼

[@LawnCareBusinessSuccess]

Glad you found value in the video. Thanks for watching.

[@bottmar1]

Flap sanders are only fast at first and that is not very long. Once they wear a little bit all they do is polish. Also they cost far more than grinding wheels, up to five times as much. I quit using flap discs for sharpening lawn mower blades years ago. Flap sanders do leave the surface extremely nice though. I only use flap sanders where I want sheet metal butt welds perfectly flat accross the welded areas. Even there, new flap discs lose their ability to provide a flat surface, quickly and long before the thickness of the disc is very thin. I do a lot of sheet metal replacement on collector cars.

[@DenCoDave]

By the direction that the sparks are flying, I would consider a different orientation of the grinder to the blade so that the grinding rotation would have sparks coming off of blade. The way shown might have the rotation of the wheel catching the blade edge and having things quickly flying about. The rotation shown here is going to be cooler for the metal at the cutting edge, but would guess that's not much of a practical issue.

[@LawnCareBusinessSuccess]

Thanks for watching and sharing.

[@michaeldahm214]

The problem with grinding off the blade is you can get a rougher edge or “paper” edge. Grinding in the direction of the blade gives support to the edge (by the thick material of blade) so you are able to get the edge sharper.

[@inhocsigno9151]

I use an angle grinder, but I have a lot of nicks due to rough ground. Also, I hold the grinder so disk rotation is toward the blade edge, not pushing into the edge in your example. With the flap disk, if rotation is wrong, the disk would be destroyed, I suppose. Never used one.

[@Jayman001]

Good educational video😂 thnx! For doing the comparison vids

[@LawnCareBusinessSuccess]

Thanks for watching.

[@joec2442]

This method of using an angle grinder is dangerous and hopefully people will follow a safer method

[@ryanramey-b3r]

You only sharpen one side of those blades sir, they're gonna get awful dull awfully quick when you make that blade cutting surface that thin, this looks very dangerous, safety is important, don't skip through safety to make it quicker, it only takes one time to catch a hot piece of metal in your eye, or cut your own fingers off, it happens more than it should

[@tcruz86]

Excellent and detailed instructional video. Liked and subscribed. Great teacher. Like the “divot” comments👍🏽Golfer? My game. Cheers!

[@joefriday950]

Great video. Thanks

[@LawnCareBusinessSuccess]

Glad you found value in the video. Thanks for watching.

[@zeekzimmerman8755]

only need to go across it once or twice not 500

[@saucebox11]

ill be tring this, thank you

[@Quality1lawncare]

Flap disc with the all American sharpener!

[@LawnCareBusinessSuccess]

Nice. That all American sharpener seems like a nice unit.

[@johnslawncaretips4103]

40 grit flap disc the best way to sharpen your blade

[@LawnCareBusinessSuccess]

Nice. 👍 thanks for sharing and watching.

[@John87219]

I use a flap disc, I use a 60 grit. Been doing it for years, never had any problems.

[@ALNTV1541]

Flap disc less likely to heat the blade and cause temperament problems.

[@meegstomtom]

I use the flap wheel. And sharpen same as you do. I do have a jig for them as well. But only use that if I hit something or after spring/fall clean ups where I get lots of sticks and suck.

[@LawnCareBusinessSuccess]

Nice 👍 I’m amazed I’m only discovering the flap disc now! 😂 Thanks for watching.

[@richardvacanti9428]

Very, very poor video your sharpening your lawnmower, blade in your hand. What your grinder that’s an accident waiting to happen what are you doing and you’re setting a bad example for people on TV what if someone did that and they cut their finger off it would be your fault

[@michaeldahm214]

Like him I’ve been doing this all my life (except for first few months learning). So do it the way that is relevant to your level of skill and strength with a tool. Yes put it in a vice if you don’t do this for a living or you only sharpen in your work shop.

[@kicko61]

NOTICE: new lawn mower blades are NOT sharp it is against the law to sell sharp blades,hoes, or any tool that you can cut yourself with in a store! You need to sharpen them BEFORE fitst use. The stores do not tell you this.